WASHINGTON – Just six feet will separate Kamala Harris and Donald Trump on the debate stage tonight, but their communication styles and policy preferences will reveal a miles-wide gap between the two as viewers size up the 2024 White House contenders.

Vice President Harris and former President Trump will meet for the first time when they share the stage at the National Constitution Center in Philadelphia. It could also be their only debate.

On the eve of the ABC News-hosted showdown, both candidates expressed confidence. But the two took strikingly different approaches to preparation. Harris focused on intensive rehearsals for days, while Trump held informal policy meetings.

Both hope to find a way to portray each other as unacceptable to voters and thus get on each other's nerves.

“This could be the biggest confrontation Philadelphia has seen since the 'Rocky' movies,” said Josh Boak of the Associated Press.

Tuesday's face-off was originally scheduled to be the second debate between Trump and President Joe Biden. That was before Biden dropped out of the race in July and endorsed Harris as his successor.

After weeks of haggling, the two campaigns finally agreed on the rules for the 90-minute showdown. These include no opening statements and no live audience, two commercial breaks and two minutes for questions, rebuttals and closing statements.

Trump won the coin toss and will have the last word. He chose to speak last in closing arguments. Harris chose the podium that appears on the right side of the screen. As a member of the incumbent party, Harris will be introduced first.

“There is a lot at stake as the race is close for both candidates,” Boak added.

After weeks of Harris climbing in the polls, those numbers now reflect a close campaign. Trump continues to hold a narrow lead over Harris among likely voters, 48% to 47%. That's within the margin of error of the New York Times-Siena College poll, meaning the race is essentially tied.

Tens of millions of viewers are expected to tune in, but Nathan Gonzales, editor and publisher of Inside Elections, told CBN News that the candidates are primarily looking to reach independent voters, especially in swing states.

“I don't expect anything to happen that will cause Democrats to turn away from Harris or Republicans to turn away from Trump,” Gonzales said on the CBN show Faith nation“I think we have settled on a core group in the middle in seven key states.”

Although Harris has enjoyed much enthusiasm and momentum since her victory at the top of the electoral list seven weeks ago, Trump could have the edge in the Electoral College.

Nate Silver, editor-in-chief of FiveThirtyEight, gives the former president a 63.8 percent chance of receiving the majority of votes in the Electoral College, which ultimately decides the race for the White House.